Injection systems for direct fuel injection in two stroke diesel engines are for example disclosed in Jikkaisho No. 62-57733 and Tokkaihei No. 1-315631 published by the Japanese Patent Office.
In the case of direct injection in these engines, fuel was injected into the combustion chamber in the latter half of the compression stroke. Due to the short period between the fuel injection and ignition, however, the injected fuel was apt to be insufficiently converted to fine particles, not well dispersed throughout the combustion chamber and poorly mixed with air. This led to poor fuel consumption performance and reduced power, and an undesirable composition of exhaust gases.
In a two stroke diesel engine, exhaust and intake valves are opened in the same down stroke of the piston and the scavenging efficiency of burnt gas is naturally lower than a four stroke engine. This also deteriorates the performance and exhaust gas composition of a two stroke diesel engine.